1. Field of the Invention
This invention relates to beam lead flexible circuits and particularly to a process for fabricating the circuits.
2. Descripton of Prior Art
There exists a need for developing techniques for fabricating beam leaded flexible interconnections capable of being connected to all types of device chips including those manufactured in low volume. Integrated circuit chips are usually very small and include a plurality of minute wires that require bonding to external package heads. Presently, interconnections in devices are made utilizing flying leads. This technique is time-consuming, tedious and the fragile wires are easily broken during the various handling steps in assembly. Flying leads also pose another problem in that they are non-planar, therefore, when utilized in devices such as bubble memory devices they cause noise in the memory, i.e. dQ/dT pickup.
Another known art technique, the beam leaded flexible circuit, is disclosed in U.S. Pat. No. 3,689,991, entitled "Method of Manufacturing a Semiconductor Device Utilizing a Flexible Carrier" by A. D. Aird. This method is directed at mass production and employs a metallic foil laminated to a flexible dielectric tape. The flexible layer utilizes an adhesive to hold the metallic foil in place. The insulating layer has centrally located space apertures. These apertures are covered by the metallic foil and are structured to encompass contact regions of a semiconductor body. Leads are formed from the metallic foil within the respective apertures for contact with an integrated circuit chip. The beam leaded flexible circuit has the advantage of providing planar interconnection boards. But this technique is dependent upon the ability to provide the beam leads over a predetermined cavity into which the die or chip fits. The leads must be free of adhesive and have a surface that is capable of being bonded to the device in a suitable manner, for example, thermo-compression bonding. This known technique may not assure that the beam leaded pattern is protected from damage during lamination to the flexible layer and during the subsequent processing steps.